Sexual Orientation

Front 1

Brain development is modified by the presence of _______ which modify ________

Back 1

sex steroids / circuit organization

Front 2

talk about the development of reproductive behaviors in men and women? How and when they develop

Back 2

reproductive behaviors are sexually dimorphic, they consist of different circuits between men and women and these circuits develop at different times during life.

Front 3

The normal developmental process in the absence of steroid exposure produces a ________ in all mammals so far studied. What is the genetic evedence?

Back 3

female phenotype

Turners syndrome

Front 4

steroids have two separate types of effects.

Back 4

1) masculizing brain
2) defeminizing brain

Front 5

The absence of _______ due to a genetic defect in the production of the enzyme _______ causes males to have female genitalia but does not affect the differentiation of the male brain.

Back 5

5-alpha-dihydrotestosterone/ 5-alpha reductase

Front 6

Excessive production of androgens from the adrenals during development due to the absence of the enzyme __________ leads to development of male genitalia in genetic females and to male-like behavior patterns. (adrenogenital syndrome)

Back 6

11-beta hydroxylase or 21-hydroxylase

Front 7

The aromatization of testosterone to estradiol requires the enzyme _______ _________ may be required in some neurons for changes in growth and development to take place.

Back 7

aromatase / aromatization

Front 8

Vom Saal
uterine position in rodents

Back 8

a range of normal variation in degree of masculinization and defeminization

Front 9

Perinatal steroid exposure is important in the later development of heterosexual or homosexual preference.
Evidence?

Back 9

1. Males with androgen insensitivity syndrome (absence of normal androgen receptors) have female phenotypes and prefer male partners.
2. Females with elevated perinatal androgens resulting from the adrenogenital syndrome have an elevated incidence of homosexual preference.
3. Laboratory studies in rodents indicates that perinatal castration in males results in homosexual preferences in adulthood.
4. Male preferences are probably the result of normal pattern of development in both sexes unless the process is side-tracked by exposure to androgens during early development.
5. Psychosexual predispositions established during early development may be either reinforced or altered by learning processes during childhood, e.g., gender role assignment.
6. Maternal stress is associated with the later development of homosexual preference in male fetuses.

Front 10

Other factors found or thought to be due to perinatal androgen exposure

Back 10

agressiveness
maternal responsiveness
cognitive function

Front 11

Homosexual orientation is a product of the interaction of genes and environment.

Back 11

A. Dean Hamer et al at NIH have shown that homosexual orientation in males is linked to a gene on the X-chromosome.
B. Family studies and twin studies demonstrate genetic components to both male and female homosexuality.
C. Environmental variables related to male homosexual outcome include maternal age, perinatal stress, paternal availability, peer competition.
D. Birth order of male homosexuals is higher than matched controls, and this difference is accounted for by a larger number of older brothers.

Front 12

inclusive fitness

Back 12

Non-reproductive strategies for promoting survival of ones genes

Front 13

Parental Investment Theory

Back 13

Prediction of low or high fitness for offspring is possible early in development (prenatal).
2. Genes for alternate reproductive strategies may be favored when some individuals have a low probability of survival/reproduction.